Between the 17th of Tammuz and Tisha B'av
13. When Rosh Chodesh Av falls on a Friday, a person who is accustomed to
washing with hot water every Friday (in honor of Shabbos) may also wash
with hot water on that day. On the Friday before [the Shabbos preceding
Tish'ah B'av,] "Erev Shabbos Chazon," even a person who usually washes
[with hot water] on Friday is forbidden to wash [his entire body] with hot
water (1). He may, however, wash his face, hands, and feet (2).
Similarly, a person who washes his hair [with hot water] every Friday may
do so [on Erev Shabbos Chazon]. He is not allowed to use soap or lye
(3). A person who immerses himself [in the mikveh] every Erev Shabbos, may
immerse himself in an unheated [mikveh] on Erev Shabbos Chazon as
well. Nevertheless, if a person is sometimes lax about observing this
custom (4), he is forbidden to immerse [on Erev Shabbos Chazon].
(1) Even cold water may not be used on Erev Shabbos Chazon to wash one's
entire body (Mishna Berura 551:95).
(2) Even with hot water, providing he is accustomed to do so every Erev
Shabbos (Ibid. 97). There are recent authorities who rule that since
nowadays we are accustomed to bathe more frequently, one may bathe normally
(that is, wash the entire body) even with hot water on Erev Shabbos Chazon,
if he is accustomed to do so on every Erev Shabbos.
(3) According to the authorities mentioned in note (2) who permit regular
bathing in hot water on Erev Shabbos Chazon, one may use soap and shampoo
on one's hair as well, provided that one is accustomed to do so every Erev
Shabbos (Rav Shimon Eider: "Summary of the Halachos of the Three Weeks").
As we noted in HY 122:12, soap and shampoo may be used during the rest of
the nine days, only when they are essential for removing dirt and perspiration.
(4) Due to business commitments or other time constraints.